This invention relates to an apparatus with an initiator for detecting the rotational position of a shaft comprising a housing containing an electric sensor element and a movable revolving body fastened on the shaft.
Such an apparatus, which is designed as an angle of rotation detecting element, is disclosed in German patent application No. DE-OS 31 33 061. The revolving body includes a ferromagnetic part, which changes the magnetic flux between a permanent magnet and a coil according to the angular position of rotation of the shaft. The coil is a component part of the sensor element, which is in stationary arrangement in the housing and has a high-frequency oscillating circuit, the feedback to the ferro-magnetic part being influenceable. The shaft has a thread and the revolving body is fixed on the shaft by means of a nut. In production and assembly, the revolving body with the ferromagnetic part must be aligned precisely both with respect to the shaft and also with respect to the magnet system with the permanent magnet and the coil. Due to the confined space in the housing, in practice difficulties are encountered in producing the screw connection and a correspondingly high production cost results. Furthermore, in practice considerable difficulties are often encountered during assembly of such an apparatus, for example on a geared motor or on a servo drive, in carrying out an exact adjustment on site according to the installation conditions such that, on reaching an end position, the necessary signal can also actually be generated. Finally, there is the risk that the screw connection will loosen in the course of time and consequently the function of the apparatus and associated parts of the system, will be questionable.
A coupling for transmitting rotational movements without backlash, in particular for precision rotary potentiometers, is disclosed in German patent application No. DE-OS 35 36 833. An input shaft and an output shaft each have a coupling lever rotationally fixed to them. For this purpose, in each case a clamping connection is provided which has two parts which can be braced against each other by a screw and nut. In order to set and fasten the respective coupling lever on the shaft, the screws must be loosened and retightened after corresponding adjustment of the coupling levers with respect to the shaft. The final rotationally fixed connection only takes place after exact positioning and adjustment of the coupling lever and subsequent tightening of the screw connection.
Finally, a sensor apparatus for the rotational position of the drive unit of a marine propulsion system is disclosed in U.S. Pat. No. 4,722,705. A position sensor with a lever which is fastened onto a shaft is provided in a housing. The end of the lever bears against a cam, the position of which changes, for example, according to the rudder position. The lever is pressed against the cam by means of a spring. The connection between the shaft and the lever is rotationally fixed, and no self-adjustment is possible.